3com 3031 Instruccion De Instalación
Introduction to Congestion Management
947
CQ (Custom Queuing)
Figure 235 Custom queuing
CQ classifies packets into 17 classes in accordance with certain rules
(corresponding to 17 queues). Based on their own classes, packets will enter the
corresponding Custom queues with FIFO policy.
(corresponding to 17 queues). Based on their own classes, packets will enter the
corresponding Custom queues with FIFO policy.
No.0 queue is a system queue (not shown) and 1-16 queues are user queues. User
can set the rules of traffic classification and assign the proportions on occupying
interface bandwidth for those 16 user queues. During dispatching, packets in
system queue are sent preferentially till the queue is empty. Then with polling
method a certain number of packets, taken from No.1-16 user queues under the
bandwidth-occupying proportion set in advance, are sent out. In this way, packets
of different application can be assigned with different bandwidth. Therefore, it will
not only ensure mission-critical application to get more bandwidth but also
prevent normal application from obtaining no bandwidth at all. By default, the
data flow enters the No.1 queue.
can set the rules of traffic classification and assign the proportions on occupying
interface bandwidth for those 16 user queues. During dispatching, packets in
system queue are sent preferentially till the queue is empty. Then with polling
method a certain number of packets, taken from No.1-16 user queues under the
bandwidth-occupying proportion set in advance, are sent out. In this way, packets
of different application can be assigned with different bandwidth. Therefore, it will
not only ensure mission-critical application to get more bandwidth but also
prevent normal application from obtaining no bandwidth at all. By default, the
data flow enters the No.1 queue.
Another advantage of Custom Queuing is that bandwidth can be assigned
according to the busyness of applications, which is suitable for those applications
having special requirement for bandwidth. Though the dispatching for 16 user
queues is polling, the service time for each queue is not fixed. So when there are
no packets of certain classes, the CQ dispatching mechanism can automatically
increase bandwidth occupied by the packets of current existing class.
according to the busyness of applications, which is suitable for those applications
having special requirement for bandwidth. Though the dispatching for 16 user
queues is polling, the service time for each queue is not fixed. So when there are
no packets of certain classes, the CQ dispatching mechanism can automatically
increase bandwidth occupied by the packets of current existing class.
incoming packets
queue1
queue2
classify
outgoing packets
queue15
queue16
transmit
queue
interface
……
10%
30%
10%
5%
scheduler